Nobody knows how it happened: An indoor house cat that got lost on a family excursion managed, after two months and about 200 miles, to return to its hometown.

Even scientists are baffled by how Holly, a 4-year-old tortoiseshell who in early November became separated from Jacob and Bonnie Richter at an RV rally in Daytona Beach, Fla., appeared on New Year's Eve - staggering, weak and emaciated - in a back yard about a mile from the Richters' house in West Palm Beach.

"Are you sure it's the same cat?" wondered John Bradshaw, director of the Anthrozoology Institute at the University of Bristol in England. In other cases, he has suspected, "the cats are just strays, and the people have got kind of a mental justification for expecting it to be the same cat."

But Holly not only had distinctive black-and-brown harlequin patterns on her fur, but also an implanted microchip to identify her.

"I really believe these stories, but they're just hard to explain," said Marc Bekoff, a behavioral ecologist at the University of Colorado. "Maybe being street-smart, maybe reading animal cues, maybe being able to read cars, maybe being a good hunter. I have no data for this."

There is, in fact, little scientific dogma on cat navigation. Migratory animals like birds, turtles and insects have been studied more closely, and use magnetic fields, olfactory cues or orientation by the sun.

The closest, said Roger Tabor, a British cat biologist, may have been a 1954 study in Germany, in which cats placed in a covered circular maze with exits every 15 degrees most often exited in the direction of their homes.

Tabor cited longer-distance reports he considered credible: Murka, a tortoiseshell in Russia, traveling 325 miles home to Moscow from her owner's mother's house in Voronezh in 1989; Ninja, who returned to Farmington, Utah, in 1997, a year after her family moved from there to Mill Creek, Wash.; and Howie, an indoor Persian cat in Australia who in 1978 ran away from the relatives his vacationing family left him with and eventually traveled 1,000 miles to his family's home.

Still, explaining such journeys is not black and white.

Holly hardly seemed an adventurous wanderer, though her background might have given her a genetic advantage. Her mother was a feral cat roaming the Richters' mobile home park, and Holly was born inside somebody's air conditioner, Richter said. When, at about 6 weeks old, Holly padded into their carport on Christmas Eve and jumped into the lap of Jacob Richter's mother, there were "scars on her belly from when the air conditioner was turned on," Bonnie Richter said.

Scientists say that such early experience was too brief to explain how Holly might have been comfortable in the wild - after all, she spent most of her life as an indoor cat, except for occasionally running outside to chase lizards. But it might imply innate personality traits like nimbleness or toughness.

"You've got these real variations in temperament," Bekoff said. "Fish can by shy or bold; there seem to be shy and bold spiders. This cat, it could be she has the personality of a survivor."